Why Prefer Any Decision Theory?

According to LessWrong, a defense of Functional Decision Theory argues that FDT actually gives better answers than critics claim—but only if you restrict yourself to 'fair' problems. The debate centers on how agents should reason when they might be simulated by another decision-maker, as in Newcomb's Problem. The author contends that critics apply inconsistent standards to FDT while overlooking similar weaknesses in other decision theories. The key insight is symmetry: for every scenario where FDT fails, there's a mirror scenario where it succeeds. Excluding unfair or deceptive scenarios from evaluation isn't a cop-out—it's necessary because all decision theories struggle equally against an opponent willing to cheat. The takeaway: comparing decision theories fairly requires agreeing on the rules of the game.

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